Every day, thousands of cargo containers from around the world pass through our nation's sea ports carrying items we need, and possibly some that are not so welcome: drugs, explosives, chemical, biological, or radiological weapons – even human cargo.

A pivoted catch designed to fall into a notch on a ratchet wheel so as to allow movement in only one direction (e.g. on a windlass or in a clock mechanism), or alternatively to move the wheel in one direction.